U.S. patent application number 14/593657 was filed with the patent office on 2015-06-11 for system, method and computer program product for recovering stub files.
The applicant listed for this patent is KIP CR P1 LP. Invention is credited to Brian J. Bianchi, William H. Moody, II, Robert C. Sims.
Application Number | 20150161010 14/593657 |
Document ID | / |
Family ID | 52597946 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150161010 |
Kind Code |
A1 |
Sims; Robert C. ; et
al. |
June 11, 2015 |
SYSTEM, METHOD AND COMPUTER PROGRAM PRODUCT FOR RECOVERING STUB
FILES
Abstract
A read cache may include portions of files stored on media of a
media library. Embodiments described herein may include systems and
methods for restoring a read cache, including restoring stub files
to a read cache on an ad hoc basis.
Inventors: |
Sims; Robert C.; (Round
Rock, TX) ; Bianchi; Brian J.; (Cedar Park, TX)
; Moody, II; William H.; (Austin, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KIP CR P1 LP |
New York |
NY |
US |
|
|
Family ID: |
52597946 |
Appl. No.: |
14/593657 |
Filed: |
January 9, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13485060 |
May 31, 2012 |
8977827 |
|
|
14593657 |
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Current U.S.
Class: |
714/6.23 |
Current CPC
Class: |
G06F 2201/84 20130101;
G06F 11/1456 20130101; G06F 11/1435 20130101; G06F 11/2069
20130101; G06F 11/1469 20130101; G06F 16/9574 20190101; G06F 16/183
20190101; G06F 11/2058 20130101; G06F 11/1451 20130101 |
International
Class: |
G06F 11/14 20060101
G06F011/14; G06F 11/20 20060101 G06F011/20 |
Claims
1. A system for recovering a read cache comprising: a media
library, comprising: a set of drives, and a set of media; and an
archive node appliance coupled to the media library and a set of
hosts, the archive node appliance comprising a processor, a data
store and a computer readable medium storing a set of computer
executable instructions executable on the processor to: maintain a
read cache comprising portions of files stored on the set of media;
receive a request from a network file system interface client for a
first file at a first location; locate the first file at a second
location on a media of the media library, wherein the second
location mirrors the first location; read the first file from the
media of the media library; and populate the read cache with a stub
file for the first file using file data read from the media.
2. The system for recovering a read cache of claim 1, wherein the
set of computer executable instructions are further executable to
restore a set of configuration data from a backup set of
configuration data.
3. The system for recovering a read cache of claim 2, wherein the
configuration data comprises a mapping between the first location
and a third location in a data store.
4. The system of recovering a read cache of claim 3, wherein the
set of computer executable instructions are further executable to
populate the stub file at the third location.
5. The system for recovering a read cache of claim 1, wherein the
set of computer executable instructions are further executable to
respond to one or more subsequent read requests for data of the
first file using file data read from the media.
6. The system for recovering a read cache of claim 1, wherein the
set of computer executable instructions are further executable to
respond to one or more subsequent read requests for data of the
first file using file data from the data store.
7. The system for recovering a read cache of claim 1, wherein the
media library is a tape library and the set of media comprise a set
of tapes formatted according to a Linear Tape File System.
8. A computer program product comprising a non-transitory computer
readable medium storing a set of computer executable instructions
comprising instructions for: maintaining a read cache of portions
of files stored on media of a media library; receiving a request
from a network file system interface client for a first file at a
first location; locating the first file at a second location on a
media of the media library, wherein the second location mirrors the
first location; reading the first file from the media of the media
library; and populating the read cache with a stub file for the
first file using file data read from the media.
9. The computer program product of claim 8, wherein the set of
computer executable instructions further comprise instructions for
restoring a set of configuration data from a backup set of
configuration data.
10. The computer program product of claim 9, wherein the
configuration data comprises a mapping between the first location
and a third location in a data store.
11. The computer program product of claim 10, wherein the set of
computer executable instructions further comprise instructions to
populate the stub file at the third location.
12. The computer program product of claim 8, wherein the set of
computer executable instructions further comprise instructions for
responding to one or more subsequent read requests for data of the
first file using file data read from the media.
13. The computer program product of claim 8, wherein the set of
computer executable instructions further comprise instructions for
responding to one or more subsequent read requests for data of the
first file using file data from a data store.
14. The computer program product of claim 8, wherein the media
library is a tape library and the media comprise a set of tapes
formatted according to a Linear Tape File System.
15. A method for recovering a read cache comprising: maintaining a
read cache comprising portions of files stored on media of a media
library; receiving a request from a network file system interface
client for a first file at a first location; locating the first
file at a second location on a media of the media library, wherein
the second location mirrors the first location; reading the first
file from the media of the media library; and populating the read
cache with a stub file for the first file from file data read from
the media.
16. The method of claim 15, further comprising restoring a set of
configuration data from a backup set of configuration data.
17. The method of claim 16, wherein the configuration data
comprises a mapping between the first location and a third location
in a data store.
18. The method of claim 17, further comprising populating the stub
file at the third location.
19. The method of claim 15, further comprising responding to one or
more subsequent read requests for data of the first file using file
data read from the media.
20. The method of claim 15, further comprising responding to one or
more subsequent read requests for data of the first file using file
data from a data store.
21. The method of claim 15, wherein the media library is a tape
library and the media comprise a set of tapes formatted according
to a Linear Tape File System.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of, and claims a benefit
of priority under 35 U.S.C. 120 of the filing date of U.S. patent
application Ser. No. 13/485,060, filed on May 31, 2012, entitled
"System, Method and Computer Program Product For Recovering Stub
Files", the entire contents of which are hereby expressly
incorporated by reference for all purposes.
TECHNICAL FIELD
[0002] This disclosure relates to recovering stub files. Even more
particularly, this disclosure relates to recovering stub files used
to respond to requests for file data while a tape is loaded.
BACKGROUND
[0003] Businesses, governmental organizations and other entities
are increasingly saving large volumes of data necessary for daily
operations. This data represents a significant asset for these
entities. Consequently, data loss, whether accidental or caused by
malicious activity, can be costly in terms of wasted manpower, loss
of goodwill from customers, loss of time and potential legal
liability. To ensure proper protection of data for business and
legal purposes (e.g., to ensure quick recovery of data in the event
of a disaster, to comply with document retention requirements,
etc.), these entities often back up data to a physical media, such
as magnetic tapes or optical disks on a regular basis.
[0004] Traditional backup systems placed an application server,
backup server, source device, destination device and a local area
network ("LAN") in the data path of backup operations. Under these
systems, the LANs were becoming overburdened by the amount of data
being copied. Often, the backup window (the period in which data
unavailable for normal operations in order to permit backup) was
too short to achieve a complete backup of data. Accordingly, many
entities implemented Storage Area Networks ("SAN") to relieve the
burden of mass data storage and backup from the LAN, freeing the
LAN for more immediate data storage and manipulation operations. In
SANs data from multiple machines on a network may be backed up to a
remote media library. Centralized data backup allows storage
problems to be identified at one location and has the advantage of
increased efficiency.
[0005] One example of a media library commonly used in enterprise
backup systems is a magnetic tape library. In a typical magnetic
tape library, tapes are contained in cartridges and the tape
library contains multiple cartridge slots in which tape cartridges
can be stored. The tape cartridges are physically moved between
cartridge slots and tape drives by a robot. The robot is controlled
by access commands received from the host devices on the network.
When specific data is required, the host device determines which
cartridge slot contains the tape cartridge that holds the desired
data. The host device then transmits a move-element command to the
robot and the robot moves the tape cartridge.
[0006] Recently, the Linear or Long Term File System (LTFS) Format
Specification by IBM and Ultrium (hereby fully incorporated by
reference in its entirety for all purposes) has been developed,
which defines a file system for LTO-5 tapes, LTO-6 tapes and may be
extended to other tapes using an eXtensible Markup Language (XML)
schema architecture. This file system support allows the use of an
LTFS-formatted tape as if it were a file system. Files and
directories may appear in a directory listing, files may be dragged
and dropped from tape, data may be accessed at the file level,
etc.
SUMMARY
[0007] Embodiments described herein provide systems and methods for
recovering a read cache. One embodiment of a system for recovering
a read cache can include an archive node appliance. The archive
node appliance can comprise a processor, a data store and a
computer readable medium storing a set of computer executable
instructions executable on the processor. The instructions can be
executable to maintain a read cache, receive a request from a
network file system interface client for a first file at a first
location, locate the first file at a second location on a media of
a media library, read the first file from the media of the media
library and populate the read cache with a stub file for the first
file using file data read from the media.
[0008] Another embodiment can include a computer program product
comprising a non-transitory computer readable medium storing a set
of computer executable instructions. The computer instructions can
be executable to perform a method comprising: maintaining a read
cache, receiving a request from a network file system interface
client for a first file at a first location, locating the first
file at a second location on a media of a media library, reading
the first file from the media of the media library and populating
the read cache with a stub file for the first file using file data
read from the media.
[0009] Yet another embodiment can include a method for recovering a
read cache comprising: maintaining a read cache comprising portions
of files stored on media of a media library, receiving a request
from a network file system interface client for a first file at a
first location, locating the first file at a second location on a
media of the media library, wherein the second location mirrors the
first location, reading the first file from the media of the media
library and populating the read cache with a stub file for the
first file from file data read from the media.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The drawings accompanying and forming part of this
specification are included to depict certain aspects of the systems
and methods. A clearer impression of the components and operation
of systems provided will become more readily apparent by referring
to the exemplary, and therefore nonlimiting, embodiments
illustrated in the drawings, wherein identical reference numerals
designate the same components. Note that the features illustrated
in the drawings are not necessarily drawn to scale.
[0011] FIG. 1 is a diagrammatic representation of one embodiment of
system comprising an Archive Node Appliance.
[0012] FIG. 2 is a diagrammatic representation of one embodiment of
an Archive Node Appliance.
[0013] FIG. 3 is a diagrammatic representation of one embodiment of
an Archive Node Appliance.
[0014] FIG. 4 is a diagrammatic representation of one embodiment of
an Archive Node Appliance.
[0015] FIGS. 5A-5D are diagrammatic representations of one
embodiment of a schema.
[0016] FIG. 6 is a flow chart illustrating one embodiment of a
method for storing a file.
[0017] FIG. 7 is a flow chart illustrating one embodiment of
restoring a read cache.
[0018] FIG. 8 is a flow chart illustrating one embodiment of ad hoc
restoration of a stub file.
DETAILED DESCRIPTION
[0019] The systems and methods and the various features and
advantageous details thereof are explained more fully with
reference to the nonlimiting embodiments that are illustrated in
the accompanying drawings and detailed in the following
description. Descriptions of well-known starting materials,
processing techniques, components and equipment are omitted so as
not to unnecessarily obscure the description in detail. It should
be understood, however, that the detailed description and the
specific examples, while indicating preferred embodiments, are
given by way of illustration only and not by way of limitation.
Various substitutions, modifications, additions and/or
rearrangements within the spirit and/or scope of the underlying
inventive concept will become apparent to those skilled in the art
from this disclosure. Embodiments discussed herein can be
implemented in suitable computer-executable instructions that may
reside on a computer readable medium (e.g., a hard disk drive,
flash drive or other memory), hardware circuitry or the like, or
any combination.
[0020] Before discussing specific embodiments, embodiments of a
hardware architecture for implementing certain embodiments is
described herein. One embodiment can include one or more computers
communicatively coupled to a network. As is known to those skilled
in the art, the computer can include a central processing unit
("CPU"), at least one read-only memory ("ROM"), at least one random
access memory ("RAM"), at least one hard drive ("HD"), and one or
more input/output ("I/O") device(s). The I/O devices can include a
keyboard, monitor, printer, electronic pointing device (such as a
mouse, trackball, stylus, etc.) or the like. In various
embodiments, the computer has access to at least one database.
[0021] ROM, RAM, and HD are computer memories for storing data and
computer-executable instructions executable by the CPU. Within this
disclosure, the term "computer-readable medium" is not limited to
ROM, RAM, and HD and can include any type of data storage medium
that can be read by a processor. In some embodiments, a
computer-readable medium may refer to a data cartridge, a data
backup magnetic tape, a floppy diskette, a flash memory drive, an
optical data storage drive, a CD-ROM, ROM, RAM, HD, or the
like.
[0022] At least portions of the functionalities or processes
described herein can be implemented in suitable computer-executable
instructions. The computer-executable instructions may be stored as
software code components or modules on one or more computer
readable media (such as non-volatile memories, volatile memories,
DASD arrays, magnetic tapes, floppy diskettes, hard drives, optical
storage devices, etc. or any other appropriate computer-readable
medium or storage device). In one embodiment, the
computer-executable instructions may include lines of compiled C++,
Java, HTML, or any other programming or scripting code.
[0023] Additionally, the functions of the disclosed embodiments may
be implemented on one computer or shared/distributed among two or
more computers in or across a network. Communications between
computers implementing embodiments can be accomplished using any
electronic, optical, radio frequency signals, or other suitable
methods and tools of communication in compliance with known network
protocols.
[0024] As used herein, the terms "comprises," "comprising,"
"includes," "including," "has," "having" or any other variation
thereof, are intended to cover a non-exclusive inclusion. For
example, a process, article, or apparatus that comprises a list of
elements is not necessarily limited to only those elements but may
include other elements not expressly listed or inherent to such
process, article, or apparatus. Further, unless expressly stated to
the contrary, "or" refers to an inclusive or and not to an
exclusive or. For example, a condition A or B is satisfied by any
one of the following: A is true (or present) and B is false (or not
present), A is false (or not present) and B is true (or present),
and both A and B are true (or present).
[0025] Additionally, any examples or illustrations given herein are
not to be regarded in any way as restrictions on, limits to, or
express definitions of, any term or terms with which they are
utilized. Instead, these examples or illustrations are to be
regarded as being described with respect to one particular
embodiment and as illustrative only. Those of ordinary skill in the
art will appreciate that any term or terms with which these
examples or illustrations are utilized will encompass other
embodiments which may or may not be given therewith or elsewhere in
the specification and all such embodiments are intended to be
included within the scope of that term or terms. Language
designating such nonlimiting examples and illustrations include,
but is not limited to: "for example," "for instance," "e.g.," "in
one embodiment."
[0026] It may be desirable to provide a file system utilizing media
libraries. To that end, attention is now directed to systems and
methods for implementing a file system utilizing a tape library. In
particular, embodiments may present a network file system interface
to one or more host devices. These host devices may utilize the
network based file system to organize, store, read or perform other
operations in association with files. These files may be managed in
conjunction with a tape library. Specifically, commands in a
network file system protocol may be received. These commands may be
associated with operations to be performed on files, including
operations associated with the organization, storage or retrieval
of those files. Library control functionality that allows tapes in
the tape library to be tracked and tapes to be moved into and out
of drives and storage slots is utilized to manage the tape
library.
[0027] In certain embodiments, LTFS (including Library LTFS) may be
employed in conjunction with the tape library such that the tapes
in the tape library may be formatted using LTFS. Accordingly,
operations with respect to the files on the tapes in the tape
library may be performed using LTFS. A mapping may be maintained
between the files visible through the networked based file system
presented to the host devices and the corresponding location of
those files on an LTFS tape in the tape library or other location.
It should be noted here that while embodiments as discussed include
a tape library having tapes formatted according to LTFS, other
types of media libraries that utilize media of the same or
different type where the media may be formatted according to the
same or another type of file system may be employed in other
embodiments.
[0028] To increase performance, embodiments of such a system may
include a data store, which may be on a storage medium that is
relatively faster for random accesses such as a disk. Files that
are stored by the host devices using the networked based file
system may initially be stored on the disk. These files are
subsequently migrated to tapes in the tape library. Once a file has
been stored on tape, a stub file that contains a portion of the
file may remain on the data store, with the remainder of the file
being deleted from the data store. When the file is subsequently
accessed, the initial requests for file data can be serviced using
data from the stub file while the tape containing the full file
loads. The use of a stub file allows time for the tape to load and
file data to be read from the tape, reducing or preventing
timeouts.
[0029] In some cases, previously stored stub files may be deleted,
become corrupted or otherwise become unusable. Therefore, it may be
desirable to implement a stub file recovery scheme. According to
one embodiment, ad hoc stub file recovery can be implemented in
which individual stub files are recovered as needed. If a stub file
is missing, corrupted or otherwise unusable, the stub file can be
repopulated when a corresponding file is requested.
[0030] FIG. 1 is a diagrammatic representation of a system in which
a media library is managed to present a network based file system
to a plurality of hosts (i.e., host devices). Archive Node
Appliance 115 can comprise one or more communications interfaces
150, 151 (e.g., fibre channel interface, Ethernet port or any other
type of communication interface known in the art) to connect
Archive Node Appliance 115 to network 120 and network 122. In this
embodiment, hosts 110, 111, 112 and 113 are coupled to an Archive
Node Appliance 115 via network 120. Network 120 can comprise the
Internet, a LAN, a WAN, a SAN, a wireless network, or any other
communications link, network or protocol known in the art. For
example, network may comprise an Ethernet based network employing
TCP/IP.
[0031] Archive Node Appliance 115 is coupled to media library 130
via network 122 (Archive Node Appliance 115 and media library 130
may be collectively referred to as an Archive Node or a Networked
Attached Tape Archive (NATA)). Network 122 can comprise the
Internet, a LAN, a WAN, a SAN, a wireless network, or any other
communications link, network or protocol known in the art. For
example, network 122 may comprise a fibre channel network (such as
a fibre channel SAN) or a SCSI bus, such as a Serial Attached SCSI
(SAS) bus. While Archive Node Appliance 115 has been depicted as a
standalone device in this embodiment, it should be understood that
Archive Node Appliance 115 can be implemented in a variety manners
and in a variety of architectures. For example, when implemented in
a SAN, the Archive Node Appliance may be part of a router, part of
a media library or at any other location in a communication path
between hosts and a media library.
[0032] Media library 130 may comprise a tape library or another
media library known in the art such as optical jukeboxes. A tape
library, as would be understood by one of ordinary skill in the
art, typically consists of one or more tape drives that can
read/write data from/to magnetic tape (contained within cartridges
also referred to herein as tapes or tape cartridges), eject tape
cartridges and perform other operations. A series of slots stores
the tape cartridges when they are not in a drive and a robot moves
the magnetic tape cartridges between the drives and slots.
[0033] As an example, media library 130 can comprise drives
131-133, robot 134 and slots 135 (individually slots 135a-j). It
should be noted that a media library that employs a single robot or
multiple robots in an expandable or modular configuration, but
presents itself as a single media library to a network, or any
other configuration of one or more media libraries, either physical
or virtual, that can present itself as a single media library can
be considered a single media library for the purposes of this
application. It will also be noted that though the embodiment
depicts only a single media library, other embodiments may be
coupled to, and utilize, multiple media libraries.
[0034] Archive Node Appliance 115 comprises a computer processor
152 and a computer readable memory 154 (e.g., RAM, ROM, magnetic
disk, optical disk and/or any other computer readable memory known
in the art) that can store computer instructions 155 that are
executable by processor 152. Computer instructions 155 can be
implemented as hardware, software, firmware, some combination or in
any other suitable manner as would be understood by those of
ordinary skill in the art.
[0035] In operation, computer instructions 155 can be executable
such that Archive Node Appliance 115 can present a network based
file system (i.e., a file system accessible over a network) to
hosts 110, 111, 112, 113, allowing these hosts to organize, store
or retrieve files or perform other operations associated with a
file system. Operations that can be performed using such network
based files systems are understood by those of skill in the art.
This network based file system may be for example, a Network File
System (NFS) based file system, a Common Internet File System
(CIFS) based file system, a File Transfer Protocol (FTP) based file
system, a Secure Copy Protocol (SCP) based file system, a
Representational State Transfer (REST) based file system, or a file
system based on any another type of protocol which allows a file
system to be accessed over a network.
[0036] Computer instructions 155 may thus be executable to
implement operations associated with the presented network based
file system in conjunction with media library 130. More
specifically, in one embodiment, drives 131, 132, 133 may be LTO-5,
LTO-6 compliant drives and tapes in media library 130 may be
formatted according to LTFS (as disclosed in the Linear Tape File
System Format Specification Version 2.0, or other version by IBM,
hereby incorporated by reference in its entirety). In other
embodiments the drives may be compliant with other types of tapes
and the tapes may be formatted according to other tape file
systems. Computer instructions 155 may be executable to store files
received through the networked based file system on the LTFS tapes
in the media library 130 and maintain mapping information between
the files visible through the network based file system and the
location of those files in the media library.
[0037] The files visible through the network based file system can
be files stored at an intermediate location (e.g., a disk based
data store or memory). When a file visible through the network
based file system is accessed, computer instructions 155 can be
executed to provide access to the file from the intermediate
location. File operations can thus occur on the file at the
intermediate location rather than directly on the file on the
tape.
[0038] In some cases, the file may not reside or reside entirely in
the intermediate storage when the file is accessed. Therefore, the
computer instructions 155 can also be executable to determine the
location of the accessed file in the media library 130 using the
mapping information, locate and load the correct tape into a drive,
and use LTFS to mount the LTFS file system on the tape and access
the file to, for example, read the remainder of the file into the
intermediate storage.
[0039] To increase performance, in some embodiments, it may be
desired to store files on computer readable memory 154 when they
are initially received, and migrate these files to the media
library 130 at a later point. Computer instructions 155 may
therefore be executable to store files stored by hosts using the
network based file system to the computer readable memory 154. At
some later point, the computer executable instructions 155 may be
executable to migrate the file from the computer readable memory
154 to the media library 130. In this case, computer executable
instructions 155 are executable to maintain mapping information
between the files visible through the network based file system and
the location of those files on the computer readable memory 154 or
the media library 130.
[0040] The use of LTFS in conjunction with the media library 130
can afford a number of advantages when employed by an Archive Node
Appliance 115 to implement a networked based file system. One
important advantage is that the file system structure presented
through the file system may be substantially mirrored on the tapes
of the media library 130. Accordingly, if there is a failure of the
Archive Node Appliance 115 or media library 130, the files on the
tapes of the media library 130 may be easily located, as they are
stored according to a structure that is substantially identical to
that defined by the users at the hosts using the network based file
system.
[0041] Furthermore, the use of LTFS means that tapes on which files
of the network based file system are stored may be mounted and the
file system on these tapes accessed, using any computing device
which supports LTFS. As LTFS is commonly provided for many of
today's operating systems, these tapes (and files stored thereon)
may be easily accessed, allowing files to be restored or otherwise
manipulated without requiring specialized software.
[0042] To put a finer point on some of the advantages offered by
embodiments disclosed herein, the functionality and performance of
a network based file system may be achieved while simultaneously
achieving the benefits of storage on a medium typically used for
backup without the need for any type of specific backup
application. The use of an Archive Node Appliance may abstract the
media library to implement a network based file system and hide the
corresponding complexity entailed by the use of such a media
library. By using a computer readable memory which is relatively
faster for random accesses such as a disk in conjunction with the
media library to provide the network based file system the Archive
Node Appliance may provide the speed customarily associated with a
network based file system by masking the latency of the use of the
media library. Simultaneously, the use of such a media library
provides the benefit of having files automatically stored on a
storage media typically used for backup without specific action by
users or the use of a backup application.
[0043] Furthermore, the use of LTFS in conjunction with the media
library allows the file system created by users using the network
based file system to be mirrored on the storage media. Thus, when
restoring files from the storage media of the media library in the
event of a failure, no specialized structural knowledge is
required. The files on the storage media are in the locations where
they were placed by the users in conjunction with the network based
file system. Moreover, since LTFS is commonly supported data on the
storage media may be easily accessed without the need for
specialized software such as a backup application.
[0044] It may be helpful here to illustrate architectures for
certain embodiments of an Archive Node. FIG. 2 depicts one
embodiment of an architecture for an Archive Node that may be used
in instances where relatively lower capacity is desired. Here, the
Archive Node Appliance 200 may comprise one or more Gigabit
Ethernet ports 210. These Gigabit Ethernet ports 210 may be
dedicated to providing a user interface or for a systems management
interface such as the Intelligent Management Platform Interface
(IPMI). The Archive Node Appliance 200 may also comprise one or
more Ethernet ports 220 for data connections. These Ethernet ports
may be 10BASE-T, 100BASE-TX, 1000BASE-T, 10GBASE-LR, 10GBASE-LW,
10GBASE-LRM, 10GBASE-ZR, 10GBASE-LX4, 10BASE-CX4, etc. or may be of
a mixture of types. In operation these Ethernet ports 220 may be
coupled to hosts, such that a network based file system may be
provided by the Archive Node Appliance 200 and hosts may interface
with the Archive Node Appliance 200 using these Ethernet ports 220
to utilize the network based file system, for example, by storing
or retrieving files using the network based file system. The
network based file system may be implemented using a file system
implemented in association with user space such as the File system
in User space (FUSE) file system; using a kernel-based file system
such as Ext2, Ext3, Ext4 Next3, etc.; or almost any other type of
file system desired.
[0045] Archive Node Appliance 200 also includes a data store 230.
Data store 230 may be a computer readable memory used to store
computer executable instruction, files stored using the network
based file system or other data utilized by Archive Node Appliance
200, as will be elaborated on in more detail subsequently. To
ensure some degree of redundancy or fault tolerance, data store 230
may implemented as Redundant Array of Independent Disks (RAID)
storage having around 5 TB-8 TB of available storage. Archive Node
Appliance 200 also comprises a SAS port 250 through which the
Archive Node Appliance 200 is coupled to media library 260 via a
SAS bus. Media library 260 may be an IBM TS3100 tape library having
one or more LTO-5 compliant drives 262 and capable of holding 24
tape cartridges or an IBM TS3200 tape library having one or more
LTO-5 compliant drives 262 capable of holding 48 tape cartridges.
In other embodiments, the media library may include LTO-6 compliant
drives or other types of drives.
[0046] While it should be noted that Archive Node Appliance 200 may
be implemented in substantially in any form factor desired, in one
embodiment Archive Node Appliance may be based on a rack-mount
storage format and may, for example, be contained in a chassis of a
1U, 2U or 3U form factor with the data store residing internally to
the chassis.
[0047] Moving on, FIG. 3 depicts one embodiment of an architecture
for an Archive Node that may be used in instances where relatively
greater storage capacity is required, such as in, for example,
large data installations or a cloud storage provider. In this
embodiment, the Archive Node Appliance 300 may comprise one or more
Gigabit Ethernet ports 310. These Gigabit Ethernet ports 310 may be
dedicated to providing a user interface or for a systems management
interface. The Archive Node Appliance 300 may also comprise one or
more Ethernet ports 320 for data connections. These Ethernet ports
may be 10BASE-T, 100BASE-TX, 1000BASE-T, 10GBASE-LR, 10GBASE-LW,
10GBASE-LRM, 10GBASE-ZR, 10GBASE-LX4, 10BASE-CX4, etc. or may be of
a mixture of types. In operation these Ethernet ports 320 may be
coupled to hosts, such that a network based file system may be
provided by the Archive Node Appliance 300 and hosts may interface
with the Archive Node Appliance 300 using these Ethernet ports 320
to utilize the network based file system, for example, by storing
or retrieving files using the network based file system. As noted
above, the network based file system may be implemented using a
file system implemented in association with user space such as the
File system in User space (FUSE) file system; using a kernel-based
file system such as Ext2, Ext3, Ext4 Next3, etc.; or almost any
other type of file system desired. Archive Node Appliance 300 also
includes a data store 334.
[0048] Data store 334 may be a computer readable memory used to
store computer executable instructions, files stored using the
network based file system or other data utilized by Archive Node
Appliance 300. To ensure redundancy or fault tolerance, data store
may comprise a mirrored system disk 332 comprising the computer
executable instruction and other data utilized by the Archive Node
Appliance 300 during operation and Redundant Array of Independent
Disks (RAID) storage coupled to the Archive Node Appliance 300
through SAS port 336. The RAID storage may be used to store files
associated with the network based file system and may have around 9
TB-150 TB of available storage. Archive Node Appliance 300 also
comprises fibre channel ports 350 through which the Archive Node
Appliance 300 is coupled to media library 360 via a fibre channel
switch 362. These fibre channel ports 350 may be, for example, 16,
8, 4 or 2 GB fibre channel ports. Media library 360 may be an IBM
TS3500 tape library having one or more LTO-5 compliant drives 364
and capable of holding around 20,000 tapes, a media library having
one or more LTO-6 compliant drives or a media library supporting
other types of tapes that can be formatted according to a tape file
system.
[0049] Again, while it should be noted that Archive Node Appliance
300 may be implemented in substantially in any form factor desired,
in one embodiment Archive Node Appliance 300 may be based on a
rack-mount storage format and may for example, be contained in a
chassis of a 1U, 2U or 3U form factor with the data store residing
internally to the chassis or portions of the data store, such as
the RAID storage residing external to the chassis.
[0050] Turning now to FIG. 4, one embodiment of a functional
architecture for an Archive Node is depicted. Archive Node
Appliance 400 may provide an operator interface 402 through which
the Archive Node Appliance 400 may be configured. Such an operator
interface 402 may be provided, for example, using a network based
interface such as a set of web pages or the like. Archive Node
Appliance 400 is coupled to tape library 410, comprising a set of
LTO-5, LTO-6 or other tape compliant drives some of which may be
LTFS (or other tape file system) formatted tapes. In one
embodiment, each tape in tape library 410 may be used to store data
that is compressed, data that is encrypted, data that is both
compressed and encrypted or data that is neither compressed nor
encrypted.
[0051] Archive Node Appliance 400 comprises Filesystem in Userspace
(FUSE) module 412 that may presents a file system to a local
operating system. A network file system interface module 413
provides access to all or a portion of the FUSE file system as one
or more shared volumes (e.g., as a hierarchical file system with
directories, etc.) that can be accessed using an interface that
operates according to network file system protocol 414 such as NFS,
CIFS, FTP, REST etc. Data associated with the shared volumes is
stored on one or more partitions of data store 418 (a computer
readable memory), where the structure of the partitions of the data
store 418 may, or may not, correspond to the structure of the
shared volumes or to the structure of the file system presented by
FUSE module 412.
[0052] Directory operations module 420 is configured to process any
directory operations that are received by FUSE module 412. I/O
operations module 422 is configured to process any input or output
operations involved with the reading or the storing of files
associated with the file system presented by the FUSE module 412.
These operations include, for example, the writing of files to the
data store 418, the reading of files from the data store 418, the
deletion of files from the data store 418, the reading of files
from a tape in the tape library 410 or other operations associated
with the data store 418 or tape library 410.
[0053] These I/O operations may involve the use of library control
module 434, LTFS module 424, LTFS management module 432 and index
436. The location of each tape within the tape library 410 may be
maintained in index 436 (e.g., in which slot or drive each tape is
located, in which library the tape is located if multiple tape
libraries are in use, etc.). Additionally, in one embodiment, what
type of data is stored on each tape (encrypted, compressed, neither
encrypted nor compressed, etc.) may also be maintained.
[0054] Library control module 434 is configured to control the
movement of the tapes in the tape library 410, including ejecting
the tapes from the drives of the tape library 410, and the movement
of tapes to and from slots of the tape library 410 and in and out
of drives of the tape library using the robot. LTFS management
module 432 is configured to mount or unmount the LTFS file system
on a particular tape in a drive of the tape library 410. LTFS
module 424 is configured to perform LTFS operations with respect to
an LTFS mounted file system.
[0055] Library control module 434, LTFS module 424, LTFS management
module 432 and index 436 may also be utilized by file migration
module 426. File migration module 426 is configured to move files
from data store 418 to tape library 410 based on policies 428. File
mapping module 438 maintains map 442 which correlates a file
visible through the FUSE file system to its corresponding location
in the tape library 410. Specifically, a mapping between the
location (for example the path) and name of the file with respect
to the FUSE file system, the name and location of that file in the
data store 418 and the name and location of that file on one or
more tapes in the tape library 410 may be maintained in map
442.
[0056] Policies 428 may, or may not be, user configured and may be
associated with storage of the files or the migration of files from
the data store 418 to tapes in the tape library 410. Such policies
may specify, for example, how long to wait before migrating a file
(referred to herein as a migration timeout period), whether the
files are to be replicated when migrated (e.g., stored in
conjunction with multiple Archive Nodes as will be elaborated on in
more detail), how many copies of the file to keep, where the
multiple copies are to be kept on different tapes, whether the file
is to be encrypted or compressed, etc. The policies 428 may be
defined with respect to the directories presented with respect to
the FUSE module 412 such that those policies may be defined with
respect to all files within that directory. Policy management
module 430 allows these policies to be managed (e.g., created,
updated, defined, deleted, modified, etc.) by a user or otherwise.
Policies can be defined at any level of the directory structure
provided by FUSE module 412. Because a directory presented by FUSE
module 412 may be presented as a shared volume by network file
system interface module 413, a policy that applies to the directory
may also apply to the share.
[0057] In operation then, Archive Node Appliance 400 may present a
network based file system accessible through an interface, where
the files associated with the network based file system may be
stored on the tape library 410 according to a file system structure
that substantially mirrors the file system structure of the
presented network based file system. In one embodiment, mirroring
the file system structure of the presented network based file
system means that at least a portion of the path of the location of
the file as it is stored on the tape library 410 may be
substantially similar to the path of the location of the file as it
is presented through the file system.
[0058] More specifically, users at host devices coupled to the
Archive Node Appliance 400 may perform directory operations and
store or read files using an interface for the network based file
system provided by the Archive Node Appliance 400. In accordance
with these user initiated operations, commands in the network file
system protocol 414 employed by the interface may be received at
the Archive Node Appliance 400 and implemented by FUSE module 412
with respect to the partitions of data store 418. If the command is
associated with a directory operation it may be processed by
directory operations module 420. If the command is for the storing
of a file, the I/O operations module 422 may write this file to a
location in the data store 418. Map 442 may be updated to comprise
a mapping between the location and name of the file with respect to
the FUSE file system and the name and location of that file in the
data store 418.
[0059] In one embodiment, the file is stored in the data store 418
according to the one or more policies that apply to that file. For
example, if a policy that applies to the file specifies that the
file should be compressed the file may be compressed before the
file is stored in the data store 418. Similarly, if an applicable
policy specifies that the file is to be encrypted the file may be
encrypted before it is stored in the data store 418. In certain
embodiments, a self-encrypting disk, full disk encryption or a RAID
controller which performs encryption may be utilized in conjunction
with data store 418, such that all files stored in the data store
418 may be encrypted by the disk or controller when the file is
stored to the data store 418. In such cases, all files stored to
the data store 418 may be encrypted when stored to data store 418
and decrypted when read from data store 418.
[0060] Based on one or more of the policies 428, at some later
point a file may be migrated to the tape library 410. As policies
428 may be defined based on a location associated with the
presented file system, policies associated with the location (e.g.,
directory, share, etc.) where the file is stored may be determined
from policies 428 and the determined policies applied to migrate
the file.
[0061] As the file may be received over a network, errors may occur
during the transmission of the file or the storage of the file to
the data store. To account for network errors or the like, in one
embodiment, a time period referred to as the migration timeout
period is utilized. More specifically, when a file is first stored
to the data store an amount of time equal to the migration timeout
period may be allowed to elapse before the file is migrated. As
discussed above, such a migration timeout period may be implemented
as a policy. Thus, for example, a policy defining such a migration
timeout period may be associated with a share or directory as
visible through the network based file system implemented by the
Archive Node Appliance.
[0062] In any event, once a file is selected for migration, the one
or more policies 428 associated with that file may be utilized to
migrate the file accordingly (e.g., encrypted, compressed, neither
encrypted nor compressed, whether multiple copies of the file are
to be maintained, if the file is to be replicated, etc.).
[0063] An appropriate tape on which to store the file may be
determined and located using the index 436. If the appropriate tape
is not currently in a drive of the tape library, library control
module 434 may be utilized to load the appropriate tape into a
drive of the tape library 410. More specifically, in most cases
when an LTFS tape is formatted it is specified whether the data on
that tape is to be compressed or not. Thus, the selection of an
appropriate tape may include selecting a tape that is formatted
according to a policy specified for the file being migrated (e.g.,
a tape formatted to hold compressed data may be selected if a
policy specifies the file is to be compressed, etc.), selecting a
tape that has a location associated with a location where the file
is to be stored (e.g., a directory in the path of the location
where the file is to be stored, etc.), etc. The selection of an
appropriate tape may also involve other considerations not
expressly enumerated.
[0064] The file system on the appropriate tape may be mounted using
LTFS management module 432. File migration module 426 may use LTFS
module 424 to copy the file from data store 418 to the appropriate
tape at a location on the tape which corresponds to the location of
the file as presented through the file system to the host devices
coupled to the Archive Node Appliance. After the file is copied to
the tape, all, or a portion of, the file may be deleted off of the
data store. Accordingly, the migration may entail the creation of
one or more directories on the mounted LTFS file system on the
tape, where these directories may mirror the directories in the
path where the file is stored that are visible to a user at a host
device using the network based file system presented by the Archive
Node Appliance 400. Additionally, when the file is copied to the
mounted LTFS file system on the appropriate tape, actions may be
taken to implement policies applicable to the file.
[0065] For example, if a policy that applies to the file specifies
that the file should be compressed, the media drive can be
instructed to compress the file. In one embodiment, the use of LTFS
may simplify this compression. Specifically, if a file is to be
compressed the selection of an appropriate tape formatted to store
compressed data may indicate to the LTFS module 424 that data to be
stored on the tape is to be compressed. The LTFS module 424 may
configure the drive holding that tape to compress data such that
when the file is stored to the tape using LTFS module 424 it is
compressed as it is stored.
[0066] Similarly, if an applicable policy specifies that the file
is to be encrypted, the drive can be instructed to encrypt the
file. Encryption of the file being stored may be accomplished by
the tape drive in which the appropriate tape is located.
Specifically, before mounting the LTFS file system on the
appropriate tape one or more commands (for example, SCSI or other
types of commands that may or may not include key information to be
utilized) may be sent to the drive to cause it to use encryption.
The LTFS file system can then be mounted on the tape. LTFS can then
be used to store the file on the tape while the tape drive handles
the encryption of the data transparently to LTFS.
[0067] Other embodiments may accomplish compression or encryption
of the files in different manners. For example, in one embodiment,
to speed the migration of files, Archive Node Appliance may provide
hardware support for such encryption or compression. Embodiments of
methods and systems for such encryption or compression are
discussed in U.S. patent application Ser. No. 12/025,081, entitled
"System and Method For Enabling Encryption", filed on Feb. 4, 2008,
which is hereby incorporated by reference for all purposes.
[0068] Additionally, if a policy 428 associated with the file
specifies that multiple copies of a file are to be maintained a
second tape on which to store the file may be determined and the
file migration module 426 may use LTFS module 424 to copy the file
from data store 418 to the second tape at a location on the second
tape which corresponds to the location of the file as presented
through the FUSE file system. Notice here that two separate tapes
may have the file stored using an LTFS file system path that
mirrors the path of that file as presented through the FUSE file
system. Furthermore, if a policy associated with the file specifies
that the file is to be replicated the file may also be sent to
another Archive Node Appliance.
[0069] When a command to read a file is received, map 442 may be
consulted to determine the location of the file (e.g., whether it
is located in data store 418, on a tape in the tape library 410 or
both). If the requested file is completely on the data store 418,
I/O operations module 422 may respond to the read of the file using
the file as stored in the data store 418. If the file is on a tape
(and not entirely in the data store 418), the tape on which the
file is located may be determined using the map 442. The index 436
and the library control module 434 can then be utilized to
determine if the tape is in a drive, and if not, to load the
appropriate tape into a drive of the tape library 410. The file
system on the tape may be mounted using LTFS management module 432.
I/O operations module 422 can then use LTFS module 424 to access
the file on the tape and respond to the read of the file.
[0070] It will be noted here that certain actions may be taken in
association with the read file before the file is used to respond
to the read. In particular, in certain embodiments, actions
associated with one or more policies applicable to the file may be
performed. For example, if a policy that applies to the file
specifies that the file should be compressed, the file may be
decompressed as the file is read from the tape and before the file
is used to respond to the read of the file. In one embodiment, the
use of LTFS may simplify this decompression. Specifically, the tape
on which the file is stored may be formatted to store compressed
data. The presence of this type of tape in the drive may indicate
to the LTFS module 424 that data stored on the tape is compressed.
The LTFS module 424 may thus configure the drive holding that tape
such that when the file is read from the tape using LTFS module 424
it is decompressed.
[0071] Similarly, if an applicable policy specifies that the file
is to be encrypted the file may be decrypted before the file is
used to respond to the read of the file. As LTFS may not support
encryption, in one embodiment, decryption of the file being stored
may be accomplished by the tape drive in which the appropriate tape
is located. Specifically, before mounting the LTFS file system on
the tape on which the file is stored one or more commands (for
example, SCSI or other types of commands that may or may not
include key information to be utilized) may be sent to the drive to
cause it to decrypt the file. The LTFS file system can then be
mounted on the tape. LTFS can then be used to read the file while
the tape drive handles the decryption of the data transparently to
LTFS. The file is then used to respond to the read of the file.
[0072] In many cases, however, if the file is located on tape, it
may take a relatively long amount of time to access the file. This
situation may be exacerbated if, for example the file system on the
tape is not currently mounted, the tape itself is not currently in
a drive of the tape library, the tape is currently positioned at a
location far away from the location where the file is located, etc.
These conditions can result in an access time for a file on tape
that is on the order of minutes.
[0073] Many network based file system protocols have timeout
conditions. For example, in the CIFS protocol, an OPEN or a READ
command must be responded to within 30 seconds or a timeout
condition will occur. The timeout condition may be dependent on the
type of network file systems used. In some cases, the timeout
period is negotiated between a host and file system. Thus, the
Archive Node Appliance 400 can be configured to negotiate the
timeout time with hosts. The timeout time can be set in a
configuration setting for Archive Node Appliance 400. As a result,
the time period for responding to such a command may be less than
that needed to access the file on the tape. In order to present
network based file systems based on these types of protocols such
conditions may need to be addressed.
[0074] To that end, in some embodiments, read cache 450 may be
maintained on data store 418. Read cache 450 may comprise the first
portion 452 of each file stored using the network based file system
presented by the Archive Node Appliance 400. The portion of the
file in read cache 450 acts as a "stub file," which can be
presented by the FUSE file system for example as being the full
file while some of the data of the corresponding full file is not
in the data store but is stored on tape. When a file is read, then,
if any portion of the file is to be read from tape the first
portion 452 of the read file that is stored as the stub file may be
used to respond to the read request, while the file on the tape is
located and read substantially simultaneously. Since the first
portion 452 of the file is stored in the read cache 450 on the data
store 418 it can be accessed quickly enough that a timeout on
commands can be avoided while the file on the tape is accessed. The
remainder of the file can then be read from the tape and used to
respond to the commands.
[0075] The size of the first portion 452 of each file may be user
configurable, based on system parameters, or defined in some other
manner. In one embodiment, the read cache size may be based on
directories provided by the FUSE module 412 so that all the files
within the directory are a particular size. If the directory is
presented as a share, the policy thus applies to files within the
share. In another embodiment, the size retained on read cache 450
may be dependent upon the size of blocks that may be read in a
single operation via the network file system, the set time for a
timeout and the time required to load, mount and position a tape
with the requested file.
[0076] When a host device wishes to read a file it may send OPEN
and READ commands to the Archive Node Appliance 400. I/O operations
module 422 may determine if the requested file is completely in the
data store 418 using map 442. If so, I/O operations module 422 may
respond to the read of the file using the file in the data store
418.
[0077] If however, the file is only on a tape, the tape on which
the file is located may be determined using the map 442. The I/O
operations module 422 can then initiate the load and access of the
file on the tape using the library control module 434 and the LTFS
management module 432. I/O operations module 422 delays the
response to the initial OPEN command for a time period less than
the timeout associated with the received command. In some
embodiments, this time period may be the longest time period that
does not result in a timeout occurring (e.g., 20 seconds, 29
seconds, etc.).
[0078] The host device may subsequently send a READ command for a
certain amount (e.g., 64K or a different amount) of the file to the
Archive Node Appliance 400. I/O operations module 422 can delay the
response to this READ command as long as possible without a timeout
resulting (e.g., 20 second, 29 seconds, or other time period).
After the delay, the I/O operation module 422 will respond to the
command with the data requested from the stub file. The I/O
operations module 422 may continue to delay responses to subsequent
READ commands and utilize data from the read cache 450 to respond
to the READ commands until data from the first portion 452 is
exhausted or the LTFS file system on the appropriate tape is
mounted and the file on the tape can be accessed using LTFS module.
The I/O operations module may continue to delay responses and
dynamically switch between delaying responses and not delaying
responses as needed.
[0079] In addition to delaying responses, Archive Node Appliance
400 can return less data than requested by the host. For example,
Archive Node Appliance 400 may return 1K instead of the requested
64K. Whether Archive Node Appliance 400 returns less data than the
amount requested may depend on the network file system protocol,
host operating system or other factors. Returning less data than
requested provides the advantage that the read cache can be
smaller.
[0080] When the appropriate tape is loaded, I/O operations module
422 may then use LTFS module 424 to access the file on the tape and
respond to subsequent READ commands for the file. More
specifically, in one embodiment I/O operations module 422 may
utilize LTFS module 424 to access the file on the appropriate tape
and read the file from the tape into buffer 444. Subsequent READ
commands for the file may be responded to using the data in the
buffer 444.
[0081] Furthermore, in some embodiments, in addition to reading the
file into buffer 444 the file may also be read into a file cache
460 on the data store. File cache 460 may be an area on data store
utilized for temporary storage of files and may be managed
according to almost any cache management technique desired. In
certain cases if a host does not request data of the file at a
particular rate (e.g., does not issue READ commands frequently
enough, or the READ commands do not request a certain amount of
data, etc.), after a certain number of READ commands I/O operations
module 422 may respond to subsequent READ commands for the file
using data of the file from the file cache.
[0082] In certain embodiments the opposite may also occur. More
specifically, in some instances the reading of file data to the
file cache 460 in addition to reading the file into buffer 444 may
slow the response to requests for data from the host. In this case,
reading the file data into both buffer 444 and file cache may mean
that data cannot be delivered at the rate the user is requesting
the data or may otherwise slow the response to user requests. Here,
the reading of the data of the file into the file cache 460 may be
stopped before the entire file is in the file cache such that
requests for the file may be serviced more quickly. Thus, the
portion of the file that is in file cache 460 may comprise none,
some, or all, of a file.
[0083] In one embodiment, the file may be stored in the file cache
460 by appending any portions of the file which are read from the
tape to the first portion 452 of the file in the read cache 450 if
such a first portion of the read file exists in read cache 450.
Thus, if the first portion 452 exists in the read cache 450 when
any portion of the file not comprised by first portion 452 in the
read cache is read from the tape it may be appended to the first
portion 452 already stored in the read cache 450. The entire file
may be stored in the file cache 460 when the file is read. At a
later point, if portions of the file are deleted from the file
cache 460 the first portion 452 of the file may be left on the data
store 418 such that the first portion 452 of the file is in read
cache 450.
[0084] As discussed above, stub files in read cache 450 can be used
to prevent time out errors. Read cache 450 can be populated when
the files are stored to the media library. A network file system
interface client may request to store a file (which may comprise
multiple commands in a file system protocol), where the file may be
associated with a name and a path as visible through the network
based file system implemented by the Archive Node Appliance. The
file can be stored on a location on data store 418 where the file
may have a different name and be located at a path associated with
the data store. When the file is written to a location on a tape,
the file data other than the first portion 452 can be deleted from
data store 418, leaving the stub file. The data in the read cache
450 may be stored in a manner corresponding to the format in which
the file is stored on the tape. Thus, for example, if the file is
compressed when it is migrated to tape, the read cache 450 may
comprise the first portion 452 of the file in compressed
format.
[0085] To ensure the integrity of stub files, hash codes for each
stub file can be maintained (stub file hash codes 480) and backed
up. In one embodiment, a hash code for a stub file is calculated
and stored when a stub file is created. Each time a stub file is
accessed, a hash code is generated for the stub file and the
generated hash code compared to the stored hash code for the stub
file. A difference between the hash codes may indicate corruption
of the stub file that the RAID system is reading the wrong sector
or is otherwise performing incorrectly and error processing can
occur.
[0086] Stub files in read cache 450 may be deleted, become
corrupted or otherwise become inaccessible. In a large scale fault,
for example, the entire read cache 450 may be lost (e.g., due loss
of a RAID set or other failure). Rather than restoring the entire
read cache at once, which would require high resource utilization
and a large backup capacity, read cache 450 may be repopulated as
files are accessed by clients through the network file system
interface.
[0087] Accordingly, when a file is read by a network file system
interface client and the first portion 452 of the read file is not
in read cache 450, the file may be read from tape and used to
respond to the read. The file data read from tape may be used to
repopulate the read cache 450 by storing the first portion 452 of
the file into the read cache 450 at that time (embodiments of which
will be discussed in more detail below). Furthermore, file data
from the tape can be read into file cache 460 so that the entire
file is on data store 418 as discussed above. Thus, at a later
point, if portions of the file are deleted from file cache 460, the
first portion 452 of the file may be left on the data store 418
such that the first portion 452 of the file is in read cache
450.
[0088] It may be useful to discuss embodiments of the storage of
configuration such as mapping data, index data, policies, file
meta-data, tape-library data, etc. that may be utilized by an
Archive Node Appliance. Embodiments of such storage methods and
formats may be used, for example, to store the map, index and
policies as discussed above. Preferably, mapping data, index data,
policies, file meta-data, tape-library data, etc. are stored on a
separate physical storage media from read cache 450 so that if the
storage media that stores read cache 450 becomes corrupted or
inoperable, the mapping data, index data, policies, file meta-data,
tape-library data, etc. are still available. Thus, for example,
mapping data, index data, policies, file meta-data, tape-library
data, etc. can be stored on separate RAID sets from read cache
450.
[0089] Furthermore, all or a portion of data store 418 may be
backed up to internal backup storage 470 (e.g., an internal SSD) or
external back up storage 475 (e.g., to network attached storage, a
direct attached storage array or otherwise). In one embodiment, in
order to reduce backup storage requirements read cache 450 is not
backed up. In another embodiment, stub files from read cache 450
corresponding to the most frequently accessed files (or stub files
for files meeting other criteria) can be backed up, while the
remainder of read cache 450 is not.
[0090] FIGS. 5A-5D depict one embodiment of a schema for a database
that may be utilized in conjunction with embodiment of an Archive
Node for mapping data, index data, policies, file meta-data,
tape-library data, etc. All or a portion of the database can be
backed up to external or internal backup storage to facilitate
recovery.
[0091] Turning first to FIG. 5A, one embodiment of a table schema
for the storage of data relating to files and directories is
depicted. In this schema, there is a node table 502, a storage
location table 504, a storage media table 506, a disk table 508, a
storage type table 510, a location statuses table 512, a Disk to
Tape File System (used to refer to embodiments of an implementation
of a file system using an Archive Node, also known by the acronym
DTFS) settings table 516, DTFS users table 518, DTFS groups table
520, tape drives table 522, tapes table 524 and storage method
types table 526.
[0092] Storage locations table 504 may comprise information on
locations where data can be stored in conjunction with an Archive
Node and thus entries in the storage location table 504 may be
linked to entries in the storage media table 506. Entries in
storage media may, in turn, be linked to entries in the disk table
508 that are associated with a data store of the Archive Node and
entries in tapes table 524 that are associated with tapes in the
tape library of the Archive Node. Entries in storage locations
table 504 may also be linked to entries in tape drives table 522
that are associated with drives in the tape library of the Archive
Node. Entries in the storage location table 504 may also be
associated with a state and a status as represented by entries in
the location states table 514 or the location statuses table
512.
[0093] Nodes table 502 comprises entries which are associated with
a file or a directory as presented by the FUSE file system. In
general the top level directory used by a FUSE file system of an
archive node appliance can be a universally unique identifier
(UUID) associated with the archive node appliance. Examples of such
an identifier include, but are not limited to, a serial number, a
software license number or other unique identifier. The use of a
UUID as the top level directory by archive node appliances ensures
that path names to files stored by that archive node appliance will
not conflict with the path names used at a second archive node
appliance if the tape if transferred to the second archive node
appliance. For an implementation that stores hash codes for stub
files, the stub file hash codes may be stored as part of node table
502 or elsewhere.
[0094] Entries in the node table 502 are linked with entries in the
DTFS users table 518 where these entries may represent users of the
DTFS file system (which may be defined by an administrator, based
on the network based file system implemented by the Archive Node,
etc.). Each of the entries in node table 502 may also be linked
with entries in the storage location table 504 such that a link
between an entry in the node table 502 associated with a file or
directory may be linked with one or more entries in the storage
location table 504 associated with a disk or tape where that file
or directory is stored.
[0095] In the case in which an archive node appliance is part of a
Windows Active Directory domain, active directory does not use
Unix-like user IDS and group IDs to identify users. Active
directory uses strings referred to as security identifiers (SID)
for this purpose. Accordingly, the DTFS user table 518 and DTFS
groups table 520 may include an entry for a user group SID that
links the SID to the DTFS user id and, if applicable, to the
appropriate Unix user ID (UID) and group ID (GID).
[0096] Moving now to FIG. 5B one embodiment of a table schema for
the storage of data relating to tapes and tape libraries of an
Archive Node is depicted. In this schema, there is a tapes table
524, tape locations table 532, libraries table 530, tape statuses
table 542, tape types table 540, library statuses table 562,
library states table 560, tape location types table 558, mailbox
table 538, slot table 536, tape sessions table 554, tape micro
sessions table 556, tape drive types table 546, tape drives table
534, tape drive affinities table 552, tape drive statues table 548
and tape drive states table 550.
[0097] Entries in tapes table 524 may be associated with an entry
in tape locations table 532 associated with a location of tape in a
tape library (for example, a slot, drive, etc.). Each of the
entries in tape location table 532 may be associated with an entry
in slot table 536 associated with a slot in a tape library or an
entry in tape drives table 544 associated with a drive in the tape
library. Furthermore, entries in tape locations table 532 and tapes
table 524 are linked with an entry in libraries table 530
associated with a tape library of the Archive Node (of which there
may be one or more, as discussed above). In this manner, an entry
in tapes table 524 associated with a tape can be associated with an
entry in library table 530, slot table 536 or tape drive table 544
associated with the location of that tape.
[0098] Entries in tape drive table 544 may be also linked to an
entry in tape drive types table 546 associated with a type of the
drive, or an entry in tape drive statuses table 548 or tape drive
states table 550 associated with a statuses or state of a tape
drive. Entries in tapes table 524 may also be linked to entries in
tape status table 542 and tape types table 540 associated with a
type or a status of a tape.
[0099] Turning to FIG. 5C one embodiment of a table schema for the
storage of data relating to policies applicable to directories in
an Archive Node is depicted. In this schema, there is nodes table
502, directory policies table 564, policies table 566, policy types
table 568, policy values table 570 and policy arguments table 572.
Entries in directory policies table 564 may be associated with
polices to be applied to directories (and thus to files stored in
those directories). Entries in directory policies table 564 may be
linked to entries in node table 502 associated with a directory. In
this manner, entries in directory policies table 564 associated
with policies to be applied to directories may be linked to entries
in nodes table 502 associated with a directory against which that
policy is to be applied. It will be noted that a similar schema
could be utilized to associate file policies with files, share
policies with shares, etc.
[0100] Entries in directory policies table 564 may also be linked
to an entry in policies table 566 that may be associated with a
particular policy. Entries in policies table 566 may, in turn, be
linked with an entry in policy types table 568 that is associated
with a type of policy (for example, encryption or compression
policy, number of copies to keep, replication, etc.). Thus, an
entry in policies table 566 associated with a particular policy may
be linked with an entry in policy type table 568 associated with
the type of that policy.
[0101] FIG. 5D depicts one embodiment of a table schema for
collecting data on nodes in an Archive Node. In this schema, there
is nodes table 502, ingest rates table 574 and reporting durations
table 576. Thus, entries in the node table 502 can be linked to
entries in ingest rates table 574 associated with statistics on the
creation, reception, storage, migration, etc. of a file or
directory.
[0102] FIG. 5 is provided by way of example and not limitation and
the archive node appliance may store other metadata for files,
directories, users, etc. According to one embodiment, for example,
the FUSE file system may support extended attributes that are not
used directly by the FUSE file system, but can be stored by clients
and exposed through the FUSE file system. Extended attributes for a
file or directory may be stored in the node table 502 for the file
or directory other table. For example, a media management system
may organize files based on the type of project with which the
media is associated and therefore include an extended attributes
such as project:soundtrack for files.
[0103] From a review of the above, it will be apparent that
embodiments of such Archive Nodes may provide a highly effective
manner of implementing a network based file system using a tape
library. In some instances, however, it may be desired to provide a
high level of availability or increased performance in conjunction
with network based file systems. As such, in certain embodiments
Archive Node Appliances may be clustered to provide increased
performance or a higher degree of fault tolerance as described, for
example, in U.S. patent application Ser. No. 13/109,192, entitled
"System and Method for Implementing a Networked File System
Utilizing a Media Library", filed May 17, 2011, which is hereby
fully incorporated by reference herein.
[0104] Referring now to FIG. 6, a method for storing a file using
an embodiment of an Archive Node, including an Archive Node
Appliance is depicted. At step 610 a request (which may comprise
multiple commands in a file system protocol) to store a file may be
received at the Archive Node Appliance, where the file may be
associated with a name and a path as visible through the network
based file system implemented by the Archive Node Appliance. For
example, the path of the file may be path /patient.sub.--records
and the file name may be Patient1.doc. The file is then stored on a
location on the data store of the Archive Node Appliance at step
620, where the file may have a different name and be located at a
path associated with the data store. For example, the path of the
file as stored on the data store may be /data3 and the file name
may be 550e8400-e29b-41d4-a716-446655440000.
[0105] In one embodiment, as discussed above, the file is stored in
the data store according to one or more policies that apply to that
file. For example, if a policy that applies to the file (for
example, the policy is associated with the location associated with
the network based file system where the file is stored) specifies
that the file should be compressed the file may be compressed
before the file is stored in the data store. Similarly, if an
applicable policy specifies that the file is to be encrypted the
file may be encrypted before it is stored in the data store.
[0106] The map can then be updated at step 630 to associate the
name and the path of the file as visible through the network based
file system with the path and name of the file as stored on the
data store. Thus, in this example the path /patient_records and
file name Patient1.doc, as visible through the network based file
system is associated with the path /data3 and file name
550e8400-e29b-41d4-a716-446655440000 associated with the file as
stored in the data store.
[0107] Subsequently, one or more policies to be applied to the file
can be determined at step 640. The policies may be applied in
conjunction with the migration of the file at step 650. As
discussed above, in one embodiment one policy may specify that a
migration timeout period is to be applied to the file before the
file is migrated. This migration timeout period may specify a time
period such that an amount of time equal to the migration timeout
period may be allowed to elapse before the file is migrated. Thus,
if such a policy exists the migration timeout period may be allowed
to elapse before the file is migrated.
[0108] To migrate the file, one or more tapes on which to store the
file may be determined. This determination may be based on the
policies that have been determined to apply to that file. For
example, the number of tapes determined may be based on a policy
specifying that the file is to be maintained on multiple tapes. If
so, two different tapes on which to store the file may be
determined. If a policy to apply to the file specifies that the
file is to be encrypted a tape comprising encrypted data may be
selected. Similarly, if a policy to apply to the file specifies
that the file is to be compressed a tape comprising compressed data
may be selected. Assume for purposes of example that the tape on
which it is determined to store the file has a TapeID of
AN02394.
[0109] Each of the tapes on which it is determined to store the
file can then be loaded into a drive, if it is not already in a
drive, and the LTFS file system mounted. Specifically, the tape may
be located using the index that maintains the location of each of
the tapes in the library and loaded into a drive. The file can then
be copied from its location on the data store to a location on the
tape. In one embodiment, a path that corresponds to the path of the
file as visible through the network based file system may be
created on the tape using the LTFS file system if it does not
already exist. The file can then be saved using the name that
corresponds to the name of the file as visible through the network
based file system. Continuing with the above example, the path
/patient_records may be created on the tape having TapeID AN02394
if it does not exist and the file may be saved as Patient1.doc on
this tape.
[0110] In one embodiment, before or during the copying of the file
to the mounted LTFS file system on the tape, actions may be taken
to implement policies applicable to the file. For example, if a
policy specifies that the file is to be replicated it may be sent
to another Archive Node Appliance or if a policy that applies to
the file specifies that the file should be compressed, the Archive
Node Appliance can cause the file to be stored on a compressed
tape. Similarly, if an applicable policy specifies that the file is
to be encrypted the Archive Node Appliance can cause the file to be
stored on an encrypted tape.
[0111] The map can then be updated at step 660 to associate the
tape on which the file is stored, the name and the path of the file
as visible through the network based file system, the path and name
of the file as stored in the data store and the path and name of
the file as stored on the tape. Thus, in this example the path
/patient_records and file name Patient1.doc, as visible through the
network based file system is associated with TapeID AN02394, the
path /data3 and the file name 550e8400-e29b-41d4-a716-446655440000
associated with the file as stored in the data store.
[0112] At step 670 the file, or portions thereof, may be deleted
from the data store. In some embodiments, as it is desired to
maintain the first portion of a file in a read cache in the data
store, all portions of the file except this first portion may be
deleted from the data store. It will be noted therefore, that in
certain embodiments, the path and name of the file in the map that
is associated with the file as stored in the data store may
describe the location of the first portion of the file stored in
the read cache. The steps of FIG. 6 can be repeated as needed or
desired.
[0113] Turning now to providing a file to a network file system
interface client, an Archive Node Appliance may respond to read
requests from a client using data from a stub file until the tape
containing the file is mounted and data can be provided from the
tape. However, in some cases, the read cache may be lost due to
corruption, loss of a RAID set or the like. Therefore, in order to
maintain the advantages of the stub files, the Archive Node
Appliance may restore the read cache.
[0114] FIG. 7 depicts one embodiment a method for restoring a read
cache using one embodiment of an Archive Node Appliance. At step
710 archive node configuration data such as the mapping data, index
data, policies, file meta-data, tape-library data, etc. may be
restored from backup storage if required. At step 712, the stub
files can be restored. The stub files can be restored in a variety
of manners. Stub files that were backed up can be restored from
back up while stub files that were not backed up can be restored by
reading the corresponding file from tape and storing the stub file
in the read cache. In particular, stub files may be restored on an
ad hoc basis when a network file system interface client requests
to read the corresponding file.
[0115] A stub file can be restored to the same directory location
at which the stub file was located prior to loss of the read cache.
Thus, for example, if the stub file for
/patient_records/Patient1.doc was stored at
/data3/550e8400-e29b-41d4-a716-446655440000 prior to loss of the
read cache, the stub file can be restored to location
/data3/550e8400-e29b-41d4-a716-446655440000, (which may be on a new
hard drive). In other cases, the stub file may be restored to a new
directory location. The map can be updated to associate path
/patient_records and file name Patient1.doc with the new location
in the data store.
[0116] Ad hoc restoration of stub files can be integrated with
replying to read requests from network file system interface
clients. FIG. 8 depicts one embodiment of a method for reading a
file using an embodiment of an Archive Node appliance. At step 810,
a request to read a file may be received. This request may comprise
multiple commands in a file system protocol as discussed above. The
location of the file can be determined at step 820, where the file
may be located in the data store of the Archive Node Appliance, on
a tape in the tape library or both. If the requested file is
completely on the data store (e.g., as determined at step 825), the
read and subsequent requests may be responded to using the file as
stored in the data store (step 830). The file may be completely on
the data store for a variety of reasons, for example, the file has
been stored on the data store, but a migration timeout period
associated with the file has not yet expired and thus the file has
not yet been migrated; the file has been migrated but has not been
deleted; the file was previously migrated but was subsequently read
and placed in the file cache on the data store; etc.
[0117] If the file is not completely in the data store, the tape on
which the file is located may be determined at step 840. The
movement of the tape into a drive, if needed, and the mounting of
the file system on the tape may be initiated at step 850. Further,
it can be determined if the first portion of the file (e.g., the
stub file) is in the read cache at step 860. If the first portion
is in the read cache it may be used to respond to the initial
requests for file data at step 870 and some number of subsequent
requests until the proper tape volume is mounted (see e.g., step
875). As described in U.S. patent application Ser. No. 13/267,665,
entitled "System, Method and Computer Program Product for Trickling
Data to a Host," filed Oct. 6, 2011, which is hereby fully
incorporated by reference herein, data may be trickled from the
read cache to a client to allow the tape time to load.
[0118] Prior to responding to the read request, a hash code can be
generated for the stub file and compared to a stored hash code for
that stub file. If the generated and stored hash codes for the stub
file do not match an error can be generated or other action taken.
If the generated and stored hash codes do match, the stub file may
be used to respond to the read request.
[0119] When the file system on the tape is mounted, the file on the
tape may be read and used to respond to subsequent requests for
file data at step 880. When responding to the requests for file
data using the file on the tape, the file may be read into a buffer
and data from the buffer used to respond to requests. In addition,
data from the buffer may be transferred to the data store (step
890) so that, for example, the entire file can be stored in the
data store.
[0120] If the Archive Node Appliance is responding to requests for
file data from the tape, but the client is requesting data at an
insufficient rate to maintain tape streaming, the Archive Node
Appliance may switch to using data from the file cache to respond
to requests from the client for the file data while still streaming
data to the buffer in order to populate the file cache. Thus, with
respect to network file system interface clients, the Archive Node
Appliance may switch from providing file data from the data store
to providing the file data from the tape as needed.
[0121] Returning to step 860, if there is no stub file in the data
store when a file is requested by the network file system interface
client, the Archive Node Appliance can wait for the volume
containing the requested file to be mounted (step 895). If the
requesting host does not time out, the file data may be read from
tape and used to respond to the requests for file data at step 880.
Furthermore, the file data can be stored in the data store (step
890) to populate the read cache and file cache. If the client
requests file data at an insufficient rate to maintain tape
streaming, the Archive Node Appliance may switch to using data from
the data store to respond to requests for the file data while still
continuing to populate the data store with file data from the
media.
[0122] There is some chance that a requesting client will timeout
(e.g., as determined at decision block 897) before a tape volume
can be mounted and data provided to the client. In such a case, the
Archive Node Appliance can still mount the volume so that tape data
can be read into the data store (step 890). Enough tape data can be
read and stored in the data store to populate the read cache with a
stub file corresponding to the requested file. The Archive Node
Appliance may continue to populate the data store with data read
from the media until the entire file is stored in the data store.
At a later time, a portion of the file data can be deleted from the
data store, leaving the stub file.
[0123] Thus, stub files can be recovered on an ad hoc basis by
populating the stub file when the corresponding file is requested
by a network file system interface client. In such an
implementation, resources are conserved because only the stub files
for files that are needed are recovered.
[0124] In addition to storing the stub file, a hash code for the
stub file can be generated and stored for the stub file. This can
be done once there is sufficient data in the data store to form the
stub file or after the entire file is stored in the read cache.
[0125] Although the invention has been described with respect to
specific embodiments thereof, these embodiments are merely
illustrative, and not restrictive of the invention. The description
herein of illustrated embodiments, including the description in the
Abstract and Summary, is not intended to be exhaustive or to limit
the invention to the precise forms disclosed herein (and in
particular, the inclusion of any particular embodiment, feature or
function within the Abstract or Summary is not intended to limit
the scope to such embodiment, feature or function). Rather, the
description is intended to describe illustrative embodiments,
features and functions in order to provide a person of ordinary
skill in the art context without limiting the invention to any
particularly described embodiment, feature or function, including
any such embodiment feature or function described in the Abstract
or Summary. While specific embodiments and examples are described
herein for illustrative purposes only, various equivalent
modifications are possible within the spirit and scope of this
disclosure, as those skilled in the relevant art will recognize and
appreciate. As indicated, these modifications may be made in light
of the foregoing description of illustrated embodiments and are to
be included within the spirit and scope of the invention. Thus,
while the invention has been described herein with reference to
particular embodiments thereof, a latitude of modification, various
changes and substitutions are intended in the foregoing
disclosures, and it will be appreciated that in some instances some
features of embodiments of the invention will be employed without a
corresponding use of other features without departing from the
scope and spirit of the invention as set forth. Therefore, many
modifications may be made to adapt a particular situation or
material to the essential scope and spirit of the invention.
[0126] Reference throughout this specification to "one embodiment,"
"an embodiment," or "a specific embodiment" or similar terminology
means that a particular feature, structure, or characteristic
described in connection with the embodiment is included in at least
one embodiment and may not necessarily be present in all
embodiments. Thus, respective appearances of the phrases "in one
embodiment," "in an embodiment," or "in a specific embodiment" or
similar terminology in various places throughout this specification
are not necessarily referring to the same embodiment. Furthermore,
the particular features, structures, or characteristics of any
particular embodiment may be combined in any suitable manner with
one or more other embodiments. It is to be understood that other
variations and modifications of the embodiments described and
illustrated herein are possible in light of the teachings herein
and are to be considered as part of the spirit and scope of the
invention.
[0127] In the description herein, numerous specific details are
provided, such as examples of components and/or methods, to provide
a thorough understanding of embodiments of the invention. One
skilled in the relevant art will recognize, however, that an
embodiment may be able to be practiced without one or more of the
specific details, or with other apparatus, systems, assemblies,
methods, components, materials, parts, and/or the like. In other
instances, well-known structures, components, systems, materials,
or operations are not specifically shown or described in detail to
avoid obscuring aspects of embodiments of the invention. While the
invention may be illustrated by using a particular embodiment, this
is not and does not limit the invention to any particular
embodiment and a person of ordinary skill in the art will recognize
that additional embodiments are readily understandable and are a
part of this invention.
[0128] Any suitable programming language can be used to implement
the routines, methods or programs of embodiments of the invention
described herein, including C, C++, Java, assembly language, etc.
Different programming techniques can be employed such as procedural
or object oriented. Any particular routine can execute on a single
computer processing device or multiple computer processing devices,
a single computer processor or multiple computer processors. Data
may be stored in a single storage medium or distributed through
multiple storage mediums, and may reside in a single database or
multiple databases (or other data storage techniques). Although the
steps, operations, or computations may be presented in a specific
order, this order may be changed in different embodiments. In some
embodiments, to the extent multiple steps are shown as sequential
in this specification, some combination of such steps in
alternative embodiments may be performed at the same time. The
sequence of operations described herein can be interrupted,
suspended, or otherwise controlled by another process, such as an
operating system, kernel, etc. The routines can operate in an
operating system environment or as stand-alone routines. Functions,
routines, methods, steps and operations described herein can be
performed in hardware, software, firmware or any combination
thereof.
[0129] Embodiments described herein can be implemented in the form
of control logic in software or hardware or a combination of both.
The control logic may be stored in an information storage medium,
such as a computer-readable medium, as a plurality of instructions
adapted to direct an information processing device to perform a set
of steps disclosed in the various embodiments. Based on the
disclosure and teachings provided herein, a person of ordinary
skill in the art will appreciate other ways and/or methods to
implement the invention.
[0130] It is also within the spirit and scope of the invention to
implement in software programming or of the steps, operations,
methods, routines or portions thereof described herein, where such
software programming or code can be stored in a computer-readable
medium and can be operated on by a processor to permit a computer
to perform any of the steps, operations, methods, routines or
portions thereof described herein. The invention may be implemented
by using software programming or code in one or more general
purpose digital computers, by using application specific integrated
circuits, programmable logic devices, field programmable gate
arrays, optical, chemical, biological, quantum or nanoengineered
systems, components and mechanisms may be used. In general, the
functions of the invention can be achieved by any means as is known
in the art. For example, distributed, or networked systems,
components and circuits can be used. In another example,
communication or transfer (or otherwise moving from one place to
another) of data may be wired, wireless, or by any other means.
[0131] A "computer-readable medium" may be any medium that can
contain, store, communicate, propagate, or transport the program
for use by or in connection with the instruction execution system,
apparatus, system or device. The computer readable medium can be,
by way of example only but not by limitation, an electronic,
magnetic, optical, electromagnetic, infrared, or semiconductor
system, apparatus, system, device, propagation medium, or computer
memory. Such computer-readable medium shall generally be machine
readable and include software programming or code that can be human
readable (e.g., source code) or machine readable (e.g., object
code).
[0132] A "processor" includes any, hardware system, mechanism or
component that processes data, signals or other information. A
processor can include a system with a general-purpose central
processing unit, multiple processing units, dedicated circuitry for
achieving functionality, or other systems. Processing need not be
limited to a geographic location, or have temporal limitations. For
example, a processor can perform its functions in "real-time,"
"offline," in a "batch mode," etc. Portions of processing can be
performed at different times and at different locations, by
different (or the same) processing systems.
[0133] It will also be appreciated that one or more of the elements
depicted in the drawings/figures can also be implemented in a more
separated or integrated manner, or even removed or rendered as
inoperable in certain cases, as is useful in accordance with a
particular application. Additionally, any signal arrows in the
drawings/figures should be considered only as exemplary, and not
limiting, unless otherwise specifically noted.
[0134] Furthermore, the term "or" as used herein is generally
intended to mean "and/or" unless otherwise indicated. As used
herein, including the claims that follow, a term preceded by "a" or
"an" (and "the" when antecedent basis is "a" or "an") includes both
singular and plural of such term, unless clearly indicated within
the claim otherwise (i.e., that the reference "a" or "an" clearly
indicates only the singular or only the plural). Also, as used in
the description herein and throughout the claims that follow, the
meaning of "in" includes "in" and "on" unless the context clearly
dictates otherwise.
[0135] Benefits, other advantages, and solutions to problems have
been described above with regard to specific embodiments. However,
the benefits, advantages, solutions to problems, and any
component(s) that may cause any benefit, advantage, or solution to
occur or become more pronounced are not to be construed as a
critical, required, or essential feature or component of any or all
the claims.
* * * * *